Serotonin: from sensory processing to schizophrenia using an electrophysiological method.

Serotonin plays a major role in sensory processing especially with in the primary auditory cortex. The so-called loudness dependence of auditory evoked potentials is generated by pyramidal cells of the primary auditory cortex (LDAEP) which are modulated by serotonergic projection fibers to the main regulators of pyramidal cells, i.e. GABAergic interneurons. Therefore, there are a lot of preclinical as well as clinical proofs and hints that the LDAEP may serve as a valid indicator of synaptically released serotonin, although there are also data not supporting this relationship. This is further examplified by LDAEP data in patients with different states of schizophrenia, from prodromal to the chronic state. Hereby, a strong relationship was found between LDAEP, i.e. different serotonin levels, and the negative symptoms of these groups of patients with schizophrenia. This underlines the importance of LDAEP as indicator of central serotonergic neurotransmission and its high relevance for clinical psychiatry and psychopharmacology.